Fumigant mixtures



Patented Jan. 1, 1946 FUMIGANT MIXTURES Fred W. Fletcher and Eugene Kenaga, Midland,

Mich., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Michigan No Drawing.

Application August 28, 1944,

Serial No. 551,627

3 Claims. (01. 167-39) This invention relates to fumigants and is particularly concerned with new and improved mixtures and to a method for iumigating insect infested grain.

Many volatile organic compounds have been suggested as fumigants and particularly for the treatment of stored grain. Control of insect infestation is conveniently accomplished by applying the fumigant toxicant in liquid form upon the surface of the grain and permitting the fumes to pass downwardly through the body of the stored product. However, many common liquid fumigants are selective in their action and are effective against only a few of the major grain infesting insects. Other toxicants are adsorbed or absorbed by the grain in such quantity as to impart undesirable taste and odor characteristics to flour prepared therefrom, whereby baked goods containing the flour are unpalatable. Still other suggested fumigant materials are explosive or adversely affect the germinating properties of the grain.

A particularly disadvantageous feature in the conventional use of many known fumigant compositions is the failure of the latter to control insect infestation at all levels of the stored grain. Thus a material which in laboratory or experimental operations may control common grain infesting insects at low toxicant concentrations, in large scale treatment of deep bins and granaries may give surface kill only or be effective only through the middle or at the bottom of the stored rain mass. Since the survival of even a few live insects permits the rapid build-up of the infesting organisms, such fumigants are generally unsatisfactory. To avoid the irregular results attributable to stratification of fumigant vapors, large excesses of the toxicant are frequently employed. While this may accomplish an improved kill of insects, the practice is economically unattractive and the resulting high concentrations of toxicant increase the possibility of injury to the grain.

It is an object 'of the present invention to provide a new and improved fumigant composition which will. control grain insects generally. It is a further object to provide such a composition which will not be subject to the disadvantages in use which have characterized many known materials. It is an additional object to provide a fumigant mixture which will be effective at lower concentrations than many known fumigants and will accomplish the total kill of insects without imparting undesirable properties to the treated grain. A further object is to provide a method accomplish a complete kill of insects at all levels in the grain. Other objects will become apparent from the following specification and examples.

According to the present invention, improved fumigant-mixtures are provided which comprise as a major toxic ingredient a solution of ethylene the treated grain or impart odor or taste thereto.

The compositions are substantially non-flammable.

The invention further provides a procedure whereby grain stored in bins is treated with the new ethylene bromide-carbon tetrachloride mixture to obtain an economical, efficient, and complete control of weevils, borers, and beetles. This procedure comprises introducing the fumigant mixture intothe top of a filled bin, granary, elevator, etc., and onto the surface of the grain. The vapor pressures of the new mixtures are such that a gradual distribution and penetration of the toxic fumes is obtained throughout the limits of the confining structure. The substantial absence of undesirable vapor stratification or channeling effect avoids the inconsistent control frequently obtained with many liquid .organic fumigant materials.

The proportions of the ethylene bromide and carbon tetrachloride are critical. Thus, from 2.5 to 20 parts by volume of ethylene bromide is dissolved in from 97.5 to parts by volume of carbon tetrachloride to obtain compositions exerting such action as to accomplish a complete kill ofinsects. Proportions outside this range do not share the effectiveness of the described compositions. Optimum results have been obtained with compositions containing from 2.5 to 15 per cent by volume of the ethylene bromide. With such mixtures per cent control at all levels of stored grain has been obtained under a variety of temperature conditions. A definite synergistic efiect as regards insect toxicity has been observed for these compositions.

The amounts of the new compositions required to accomplish control of insects at all levels of the stored grain are relatively small; From about 1 to 3 gallons of the mixture per 1000 bushels of grain gives complete control of common weevil and beetle pests. Even smaller amounts are effective in shallow bins or where other known fumigants are employed in combination there- Exmu 1 Varying amounts of ethylene bromide were dissolved in carbon tetrachloride to obtain liquid fumigant mixtures. These products were sprinkled on the surface of wheat stored in an airtight bin 10 feet in depth. Caged Tribolium conjusum adults (confused flour beetle) were dispersed in and through the grain at various levels prior to application of the fumigant. After application of the toxic mixture, the bin was closed and allowed to stand for 3 days. The caged insects were then removed from the grain and examined to determine the degree of control accornplished. The following table sets forth the results obtained with the several compositions.

Table I Percent i)? Amgimt Percent Percent F volume mixture ig kill at kill at g 31",, carbon per 1.000 s it. 10 it. bngmde tetigghlobusheiig oi level level e gra Gallon: 0.5 99.5 2 1 100 100 1.0 99.0 2 24 100 100 2.0 98. 2 06 100 100 2.5 07. 5 2 100 100 100 ii 0 05.0 2 100 100 100 10.0 90.0 2 100 100 100 15.0 85.0 2 100 100 100 N. 0 80.0 2 100 100 98-100 30.0 70.0 2 100 96 95 40.0 60. 0 2 100 75 94 50.0 60.0 2 100 89 56 The amount of ethylene bromide alone required to give 100 per cent kill of the insects at all levels was 6 gallons per 1000 bushels. The amount of carbon tetrachloride required to give 100 per cent kill was '7 gallons per 1000 bushels of wheat.

ExAm'Ln2 In a similar fashion, solutions of ethylene bromide in carbon tetrachloride were applied to wheat bins. for the control of rice weevil. The following table sets forth the results obtained:

Table II Percent Amount of by volume mixture Percent Pe-wmt Percent by volume when r 1 m0 swim kill at kill ethylene mm f fi km 5 it. 10 it. bromide chloride of grain level level Gallon 0. 5 99. 5 2 10 100 100 1.0 99. 0 2 92 100 100 2. 0 08. 0 2 95 100 100 2. 5 91. 5 2 100 100 100 5.0 05.0 2 100 100 100 an. 0 80. 0 2 100 100 100 no 0 70. 0 2 100 90 93 40. 0 60. 0 2 100 77 50.0 50. 0 2 100 72 76 6 gallons of ethylene bromide per 1060 bushels was required to kill 100 per cent of the insects at all levels. 7 gallons of carbon tetrachloride was required to obtain 100 per cent kill of the organism in the stored grain,

Exam 3 2.5 parts by volume of ethylene bromide and 97.5 parts of an 80-20 per cent by volume mixture of carbon tetrachloride and carbon bisulfide were mixed together. This composition was applied at the rate of 2 gallons per 1000 bushels to stored wheat for the control of Tribolium confusum and rice weevil. It was found. that the composition gave 100 per cent control of both organisms at all levels in the grain. A similar result was obtained when 5 parts by volume of ethylene bromide was mixed with 95 parts of the carbon tetrachloride-carbon bisulfide mixture and applied in the amount of 2 gallons per 1000 bushels. 5 gallons of the 80-20 carbon tetrachloride-bisulfide mixture alone per 1000 bushels was required to give 100 per cent control of the organisms at all levels in the bin.

Exams: 5

2.5 parts by volume of ethylene bromide, 5.0

:parts of methyl bromide, and 92.5 parts of carbon tetrachloride were mixed together to obtain a fumigant mixture which was per cent effective against Tnbolium confusum and rice weevil at all levels in wheat when sprayed on the surface of the grain in the amount of 0.75 gallon per 1000 bushels.

EXAMPLE 6 volume of ethylene bromide, 5.0 parts of methyl bromide, and 92.5 parts of a 75-25 per cent mixture of ethylene chloride and carbon tetrachloride were mixed together. The resultant fumigant product was applied at the rate of 1.5 gallons per 1000 bushels to wheat stored in a 10-foot bin. Cages of Tribolium confusum and rice weevil were positioned in the grain at levels of one inch, 5 feet, and at the bottom of the bin prior to treatment. The fumigant mixture was applied by sprinkling over the top of the stored product. 3 days after treatment the caged insects were removed and examined. It was found that the treatment had given 100 per cent kill of Tribolium confusum and rice weevil at all levels. The 75-25 per cent mixture of ethylene chloride and carbon tetrachloride required 5 gallons per 1000 bushels of wheat to give 100 per cent control of the organisms at all levels.

Other compositions which may be employed substantially as described in the foregoing examples for the control of organisms in stored wheat, corn, rice, barley, buckwheat,- oats, rye, etc., or for 2.5 parts by vault or chamber fumigation of insect infested articles and products, include the following:

The foregoing compositions may be applied to thetopofthebinlbysprinkling orsprayingon the surface of the grain. In such use'they are eflective not onlyagainst Tri olium conjusum and rice weevil but also against suchinsects as granary weevils. the lesser grain borer, Indian meal moth, and the like. Other toxic organic liquids which are compatible with and may be included in the compositions as described include "tr'ichloroethylene, ethylene chlorobromide, propylene chlorobromide, propylene bromide, chloroform, ethylene oxide, etc. I

We claim:

1. In a method for fumigating insect infested grain stored in bins, the step of introducing a volatile fumigant comprising asa major toxic ingredient a solution of from 2.5 'to 20 per cent by volume of ethylene bromide in carbontetrachloride in the top of the bin and onto the surface 7 of the stored grain.

2. A fumigant composition including as an active toxic ingredient a solution of from 2.5 to 15 per cent by volume of ethylene bromide in carbon tetrachloride.

3. A fumigant composition comprising a volatile liquid including a solution of from 2.5 to 20 per cent by volume of ethylene bromide in carbon tetrachloride.

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